<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            width: 100px;
            height: 100px;
            background: red;
        }
    </style>
</head>
<body>



<!-- 2, 把css样式写在head标签内部的style内,    -->

    <div>
        div
    </div>



</body>
</html>
